Steps to reproduce:

1. Mysql database
2. Create two empty hosts HOST1 and HOST2, with Zabbix agent interface
3. Create template with 3 items: 1 master item and 2 items dependent on it
4. Select all template items, click Copy, select Target type Hosts
5. Select HOST1 and HOST2 and click Copy
   Result:
   

   Undefined array key 10636 [zabbix.php:17 → require_once() → ZBase->run() → ZBase->processRequest() → CController->run() → CControllerCopyCreate->doAction() → CItemHelper::copy() → CConfigFile->{closure}() in conf/zabbix.conf.php:89]
   Undefined array key 10636 [zabbix.php:17 → require_once() → ZBase->run() → ZBase->processRequest() → CController->run() → CControllerCopyCreate->doAction() → CItemHelper::copy() → CConfigFile->{closure}() in conf/zabbix.conf.php:89]
   Invalid parameter "/3/master_itemid": a number is expected.
   

Works fine if copying only to one host.

Other way to reprroduce:
1. Select all items on the template "Linux by Zabbix agent"
2. Try to copy them to HOST1 and HOST2 together